Advice? RC re-termination delta/wye for lower kV

[spinningmagnets]

If there is a spike-up in fuel prices, and a flood of interest in E-bikes this summer (as I suspect there will be), I may buy a Kepler-drive to experiment with. The Local-Bike-Shop (LBS) is interested, and very in-touch with the nearby university community.

For a variety of reasons, I am set on 6S and a 63mm motor, the usual suspects are the Turnigy 200-kV and the Aeolian 170-kV. The original combo of choice seemed to be the 200-kV at 5S, resulting in speeds just under 30-MPH (48-k/h?). Recently, Aeolian began producing the lower 170-kV, which would allow acceptable top-speeds with the higher voltage of 6S without a major cost-bump for the ESC, batteries, or charger.

I'm told that the more time thats spent at partial throttle, the more heat is generated in the ESC due to Pulse-Width-Modulation (PWM). The college students I've polled (potential customers), prefer to stay at 20-MPH by a large margin, so I've pondered how to achieve that in the simplest and most cost-effective way. My back-of-the-envelope math suggests a kV of 120 would be near the goal at 22V-24V.

Adrian: Can't you just reterminate the windings from the current delta to wye to lower the kV? I have no idea how hard this is, but sounds a hell of a lot easier than rewinding a motor. It would also allow us to use the XieChang sensorless ebike controllers, giving us hall throttle input, current limitting, speed switch etc, right out of the box.

Berties thread encouraged me to try my hand at making RC-hall kits this summer, but Thuds posts seem to show there are still RC-hall issues to be resolved (by people smarter than me) before production should be attempted. I've been re-reading and thinking about Adrians suggestion, and It sounds pretty good.

I've considered re-winding a motor (Jeremy has been very informative and helpful) but, re-termination of delta/wye sounds much easier and faster. Can anyone verify for certain if the 170-kV and 200-kV are terminated in delta from the factory, would wye lower the kV? and also, which kV (200/170?) is the most likely candidate to achieve 20/22-MPH using 6S (22V-24V)?

Thanks in advance,...and I'll mail a free Endless-Sphere sticker for the best answer!

 

[Thud]

good evening spin,

I can say the issue is not hall sensors....its is all simple really.
I really hope I havent scared anybody off trying the xie chang controllers...remember I am attempting to run this stuff in the last 2% of the operational envelop. With the biggest & baddest motors (from the controllers standpoint)

To answer your question, The turnigy 63m are definatly terminated in Delta. (I am rewinding one this week in fact) my 20" bmx was last run on a 6fet xiechang & a 63/54-250kv motor. although I can feel the curent limiter stalling my "ultimate" hgh speed peerformance...The bike works really well with that set up & is a ton of fun in the woods behind the house. & still good for 18mph on the street with my current gearing set up. I last ran it on 12 cells.

I can't imagine re-terminating the stock windings (on a turnigy anyway) they have a bunck of epoxy overspill in the front stator area & it pretty much destroys the winding integrity when you seperate the stock phase terminations.

The bigger issue is controller mods for the lower voltages, but Jeremy & a few others have that handled in the tech section.
I will get the measurments & wind specs for the 63/64-280 I am re-winding for a friend.(need to pick up some 16g for that one)
Good Luck & take care.

 

[spinningmagnets]

Thanks for the info, Thud, I read every post of yours and have ear-marked many. Your contributions are very inspiring!

 

[Kepler]

Just keep in mind that although 100% throttle is best as far as PWM switching is concerned, even 70% isn't too hard on the controller under load. Dont get too hung up that you need to keep the ESC 100% to avoid burn out. I recon the 170kv motor is going to be at about 80% for 20mph. No problem with that especially since you dont need that much current to go 20mph (except if its a decent hill of cause)

Bring a bit of current limiting into the equation at lower speeds, and all bases are covered. Even if you are using a simple servo tester interface, a simple resistor in series to limit the throttle signal works well to limit the speed to 80%

 

[Jeremy Harris]

What I've found is that all of the RC outrunner motors I've looked at are terminated as delta and that some can fairly easily be changed from delta to wye and some are much harder to change.

It all depends on how thin the wires are and how they are soldered together when they leave the motor. If you have a motor with long "tails" of winding wire leading outside, with the soldered joint to the connectors or silicone leads some distance from the base, then it is usually easy to change the wiring over (maybe an hour's work, maximum). If the wires are very thin and the soldered joint is close to the motor base then it can be very difficult, if not impossible, to change the configuration.

With a motor with long winding tails, the process is to strip off the heatshrink sleeving, un-solder the connector or silicone lead and then carefully unsolder and separate all of the individual winding strands, taking care not to break any. The aim is to separate out each phase bundle into two separate bundles, one for each winding. Sometimes you can see these bundles as separately twisted groups, just soldered together at the joint. If this is the case then separation is easy, with no need to separate out individual strands.

If you do need to separate individual strands, then you need to identify which is which. In each bundled phase half the wires will be winding starts for one winding and half will be winding ends for the adjacent winding. The aim is to separate out all the wires, keeping them loosely grouped as phase bundles and identify (using a continuity tester or meter) which wires are the starts and which are the ends.

Once this is done you will have 6 groups of wires, three starts and three ends. Connect all the end wires together for all three windings and then connect all the wires in each group of starts together as three separate leads. The three groups of starts become the new phase wires. It doesn't matter which you label start and end, as long as its consistent for each split phase. Drawing a diagram may help with keeping track of which wire is which.

Jeremy

 

[spinningmagnets]

Thanks Kepler and Jeremy for the replies, I appreciate the good work that both of you are doing, and how generous and "open-source" you've both been. I just had a quick chat with Matt, and he was also very helpful concerning several issues. Off the top of his head, he estimated that starting with the 200-kV would result in about a 130-kV. So, that motor might be the best candidate if I attempt D/W re-termination.

Matt mentioned that due to his extensive data-logging (and pile of smoking ESCs) that the graphs show the worst PWM heat and voltage spikes were around a 25% throttle under heavy load. Though, other posts have mentioned that anything under 50% throttle was an "area of concern".

So now, I am weighing a 170-kV with current-limiting to 20-MPH (80-ish % throttle) and possibly active cooling...against a re-terminated 200-kV (resulting in 130-kV). And, both options seem much easier and faster to me than rewinding a 63mm motor. Thanks to all!

Edit: do RC-outrunners operate cooler in Delta or Wye? Would the optimum ESC settings need to be changed if re-terminated in Wye?